The present invention relates to an article produced by forming an inorganic thin film on an organic film, which is particularly applicable as a functional film by dispersing inorganic particles having a photocatalytic function, an antistatic function, and/or a light reflectance changing function in the inorganic thin film; a process for producing the article; and a product using the article.
An attempt has been made to coat an organic film with an inorganic thin film for enhancing the optical function of the film, as disclosed in a document "New Glass, Vol. 13, No. 3, p. 25 (1989)". Such a film has been known as a transparent conductive film. The coating of the inorganic thin film has been performed by sputtering.
Japanese Patent Laid-Open No. Hei 6-139964 discloses a cathode-ray tube with a functional film. The function film, which is produced by forming a thin film having a antireflection effect or a wavelength-selective absorption effect on a basic film, is adhesively bonded on a CRT. More specifically, the functional film is produced by forming a multi-layered thin film on the basic film by vacuum evaporation. However, there is disclosed a process of producing such a functional film by coating a basic film with a sol solution by spray coating.
A technique of producing a tile and the like having an antibacterial effect using a film having a photocatalytic function has been known, for example, from a document "FC Report, Vol. 113, No. 7, p. 195 (1995)". In this technique, a heat-resistant substrate such as a glass substrate or a tile is coated with a sol of titanium oxide, and is subjected to heat treatment at several hundred .degree.C., whereby a titanium oxide thin film having a photocatalytic function is formed on the substrate. Also, there has been known a refrigerator including an ozone deodorizing device capable of decomposing malodorous components in the refrigerator.
A process of forming an inorganic film on a basic film by sputtering or vacuum evaporation has problems in requiring a large-scaled vacuum apparatus, being unsuitable for formation of a large-area film, and being high in cost of film formation. Sputtering has another problem that since a thin film is formed in argon plasma, the film is possibly destroyed due to reverse sputter of the film by argon plasma.
As the other film formation process, CVD (chemical vapor deposition) has been known. The CVD process, however, has a problem in that it is difficult to form an inorganic film on a large-area basic film because of a high film formation temperature. In particular, it is difficult to form an inorganic film on an organic film having a low heat resistance by the above-described known process.
A technique may be considered, in which an inorganic film is formed on the surface of a basic film by vacuum evaporation while cooling the surface of the basic film; however, such a technique requires a considerably special attachment device. Further, an inorganic thin film formed by vacuum evaporation is very weak in strength in the lateral direction of the film because the film has a columnar structure.
On the other hand, there has been known a technique of coating a basic film with a sol solution of inorganic particles by spray coating, followed by heat treatment, to form an inorganic thin film on the basic film. The technique, however, has following problems. The surface of the inorganic thin film is liable to be uneven so that it possibly deteriorates the transmittance of light from a phosphor when used for a display unit. Further, the adhesion strength of the inorganic thin film to the organic film is very low because the organic film cannot be heat-treated at a high temperature.
CRTs of a type having an antireflection/antistatic film have been known. In most cases, such a film is directly formed on the surface of a CRT face glass. In other words, the CRT is not of a type in which an organic film on which an antireflection/antistatic film is previously formed is provided on the surface of the CRT face glass. Additionally, a process of forming an antireflection/antistatic film on the CRT face glass by spin coating or spray coating has a problem in taking a lot of labor, thereby making poor the productivity.
As for a tile or the like on which a film of titanium oxide having a photocatalytic function is formed as described above, the film is formed by coating the tile with a titanium oxide sol solution by spraying, and heat-treating the resultant tile at several hundred .degree.C. Accordingly, it is difficult to form the above titanium oxide film on an organic film having a low heat resistance and to provide the organic film on a tile.
There have been not known techniques of forming a film having a photocatalytic function to exhibit an antibacterial effect on wallpaper, a construction material, an air conditioner, a refrigerator, etc.